Heat shields protect an object or gaseous area from heat. More specifically, in many applications heat shields attempt to limit conductive, convective, and/or radiant heat transfer. Conductive heat transfer refers to the transfer of heat across a medium, whether the medium is solid or fluid. Convective heat transfer occurs between a moving fluid and a surface of an object. Radiant heat transfer occurs when excited atoms emit electromagnetic radiation, which travels from the heat source to a distant object.
One method used to protect against the transfer of heat is to place a barrier, such as a sheet of metal, which is generally thermally conductive material, between the heat source and the protected object or gaseous area. A surface of the barrier exposed to the heat source may reflect some indirect heat, but it also absorbs some of the heat. As some of the heat is absorbed, the exposed surface becomes heated. One disadvantage of this prior art is that the conductive properties of the barrier cause the surface heat to flow through the barrier by way of conduction, ultimately heating the opposing or protected shield surface. The elevated temperature of the protected surface then increases heat transfer from the protected surface of the barrier to the object or area that the barrier is trying to protect.
Efforts to reduce the effects of radiant heat include constructing barriers from thicker, reflective, or low thermal conductivity materials. Also, numerous shields of complex design have been employed. While the trend has been to develop new materials and more complex designs, the industry has lost sight of providing an improved heat shield at a reasonable cost.
The foregoing illustrates limitations known to exist in heat shields. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above.